Chinese amps have taken over that segment of the market (tube preamps, tube amps). American brands which formerly occupied that space have mostly had to move upscale (e.g. ARC, VAC), or die off. Rogue is one rare exception, that produces at any scale. Then there are a few of the small scale "one man" type operations too.
Why was the entry level line at Audio Research eliminated?
One of my first tube preamps was the SP-16. I believe it was the last preamp that founder William Z. Johnson developed. Price was around 2K-2.5K w/phono. It was an excellent reliable preamp. But now if you want a new entry level ARC it's not available. Too bad. Was it just not profitable. It was an excellent way to get into their gear and move up the ladder over time.